1. Field of the Invention
The present invention relates generally to steering linkages for automotive vehicles (including agricultural, off-highway, and recreational vehicles), and more particularly to a ball joint assembly with an over/under configuration.
2. Background
A typical automotive vehicle steering linkage includes two steering knuckles, one on each of the steered wheels, interconnected by a tie rod extending across the vehicle to force the two wheels to steer in unison. Typically, ball joints are used as the connections between the tie rod and the steering knuckles.
A drag link receives steering input from a steering gear through a Pitman arm and transfers those steering inputs to the steered wheels in one of several ways. In some designs, the drag link is pivotally connected to the tie rod at some point between the two steering knuckle ball joints. See, for example, U.S. Pat. Nos. 4,327,926; 1,551,711; and 1,726,961. It is also known to attach the drag link directly to one of the steering knuckles using a second ball joint.
U.S. Pat. No. 2,049,502 discloses a steering linkage having a tie rod with a housing at its end containing two separate ball ends and studs, one stud projecting downward to connect with a steering arm and the other stud projecting upwardly to connect to a drag link directly on top of the tie rod.
In designing a steering linkage assembly, there are a number of performance and packaging advantages to positioning the connections between the steering knuckle and the ends of the tie rod and drag link as far outboard (with respect to the vehicle longitudinal centerline) as possible. For example, this configuration maximizes the length of the drag link to reduce bump and roll steer. It is also advantageous to locate the outboard end of the drag link as far in a longitudinal direction from the wheel steering axis as possible in order to maximize the effective steering arm radius, thereby giving improved steering authority. Positioning the outboard end of the tie rod as far from the wheel steering axis as possible provides a greater moment arm which reduces the loading on the steering linkage components. It also improves packaging and enables the tie rod to extend in a straighter line between the steering knuckles, thereby reducing buckling stresses and permitting a smaller diameter rod to be used.
In all previously known steering linkages, the connection between the steering knuckle and the ball joints for the tie rod and drag link have not been configured to permit the advantageous geometries described above to be achieved simultaneously.